Fertility is a complex biological process that requires exquisite timing. At birth, the female has produced her lifetime supply of eggs. During each menstrual or estrus cycle, a few eggs will complete meiosis and undergo the final maturation process. The mature egg(s) must be fertilized by spermatozoa within a small window, usually 2–3 days, for the zygote to successfully implant within the uterus. A successful pregnancy requires the exact timing of many hormones and processes. For example, the corpus luteum on the ovary must produce progesterone to establish and maintain the pregnancy. During this time, the zygote continues development to form a blastocyst, producing chorionic gonadotrophin and developing the placenta, which will continue progesterone production. The dysregulation of fertility and pregnancy itself are highly studied processes, especially in the developed world where couples often choose to produce offspring during their later, less fertile years. These biological processes are also very important economically in the agricultural field, where livestock must be bred in an efficient manner. Male fertility can be dysregulated in a gross manner, with a lack of sperm production. However, the dysregulation is often more subtle, including structural or chromosomal abnormalities of the spermatozoa. There are many more pathways in which disruption may occur during the female fertilization process, from the maturation of the ovum to the implantation process. Potential difficulties later in pregnancy often include placental abnormalities, leading to pre-eclampsia or intrauterine growth retardation. The fetus itself can also undergo dysregulatory processes caused by carrier or spontaneous mutations. There are many methods to study the exact molecular mechanisms of these processes, with the primary goal of a successful healthy pregnancy.